1. Field of the Invention
The present invention relates to an absorbent article suitable for absorbing menstrual blood and so on discharged from a woman's genital organ, more particularly, relates to an elongated absorbent article intended to cover the wearer's body from a vaginal opening to buttocks.
2. Description of the Related Art
Absorbent articles intended to absorb menstrual blood discharged from a woman's genital organ are typically constructed to include a liquid-permeable topsheet appearing on its skin surface, a liquid-impermeable backsheet appearing on its garment surface and a liquid absorbent layer disposed between the topsheet and the backsheet, and generally, they are worn with the backsheet adhered to an inner side of a groin piece of an undergarment through a pressure-sensitive adhesive layer.
In such an absorbent article, the function of certainly collecting menstrual blood applied to the skin surface is required so as to prevent lateral leakage of liquid and rearward leakage of liquid from the absorbent article.
Particularly in an absorbent article that is intended to be worn by a woman during menstruation while sleeping, required is not only prevention of lateral leakage of menstrual blood from the absorbent article but certain absorption of menstrual blood trying to flow along the wearer's body toward the anus and the cleft of the buttocks or trying to flow along the skin surface of the absorbent article rearwardly without causing any leakage. Accordingly, such an absorbent article for nighttime use is elongated more than absorbent articles for daytime use so that its skin surface can cover a large area from a mons pubis which is anterior to the vaginal opening to the buttocks which is posterior to the anus.
In sanitary napkins of this kind, there have been known ones whose skin surface can easily fit in the woman's crotch, wherein compressed grooves are formed in the liquid absorbent layer so as to function as flexible hinges.
Japanese Unexamined Patent Publication No. 10-328233 (Patent Publication 1) discloses an elongated sanitary napkin whose rear portion can cover the buttocks of a wearer. In a front portion of this sanitary napkin, a pair of longitudinally extending topside grooves is formed in the skin surface; in a rear portion thereof, a longitudinally extending rear groove is formed in the garment surface. The topside grooves are spaced longitudinally apart from the rear groove so as not to overlap as viewed from a lateral direction. In this sanitary napkin, since the topside grooves in the front portion can function as flexible hinges, a central portion positioned between the topside grooves can be easily deformed in an arch-like state toward the wearer's body so as to come into close contact with the excretory part, and in addition, since the napkin can be easily deformed in the rear portion to bulge toward the wearer's body along the rear groove, the bulging portion can easily fit in the cleft of the buttocks.
On the other hand, Japanese Unexamined Utility-Model Publication No. 3-33622 (Patent Publication 2) discloses a sanitary napkin, in which a pair of longitudinally extending first compressed grooves is formed in the skin surface of the napkin, while a longitudinally extending second compressed groove is formed in the garment surface of the napkin at an intermediate position between the first compressed grooves in pair. This sanitary napkin can be easily deformed into a W-shaped cross section such that the central portion of the napkin is deformed at the second compressed groove to bulge toward the wearer's skin while both side portions of the napkin are deformed at the first compressed grooves to bulge toward the garment, whereby the central portion of the napkin comes into close contact with the excretory part of the wearer's body.
In the sanitary napkin disclosed in Patent Publication 1, the rear groove is formed in its rear portion so that the portion having the rear groove can fit in the cleft of the buttocks. However, since the rear portion is flat except for the rear groove, if the rear groove is pressed against the cleft of the buttocks, such as by elastic members provided centrally of a back body of sanitary shorts, portions at both sides of the rear groove tend to deform away from the buttocks due to a reaction force to the pressure given to the rear groove. Accordingly, a space is easily left between the surface of the buttocks and the rear portion of the sanitary napkin.
In the sanitary napkin disclosed in Patent Publication 2, on the other hand, the sanitary napkin can be easily deformed into a W-shaped cross section when subjected to a lateral pressure from the thighs, so that the central portion of the skin surface can easily come into close contact with the vaginal opening. However, if the construction disclosed in Patent Publication 2 is adopted for a rear portion of a sanitary napkin that is intended to contact the buttocks, the rear portion of the sanitary napkin cannot closely conform to the curved surface of the buttocks. More specifically, since the buttocks have a cleft posterior to the anus and are three-dimensionally outwardly curved at both sides of the cleft, the rear portion of the sanitary napkin that is deformed in a W-shaped cross section hardly conforms to the three-dimensionally outwardly curved surface. Therefore, leaving a space between the surface of the buttocks and the rear portion of the sanitary napkin cannot be prevented.